Is the BB OPA627 a direct replacement for the 5534? Can I just swap one out with the other? If not, what should I look at in spec sheets to tell me which to choose?
Thanks in advance.
Thanks in advance.
No, better not. If you do not understand the rest of the circuit, I cannot recommend it.
Just because the part is more expensive it is not necessarily better in any application.
The FET inputs behave much different from bipolar ones, they are much more sensitive to damage when handling. They are meant for high impedance sources, which are quite rare in Audio.
Temperature stability is not as good and the part might get hot and be unstable.
The noise is higher, especially at low frequencies .
The output swing limitation is not symmetrical and lower than the bipolar.
5534 has +/-22V max rail voltage vs. only 18V.
The transient behaviour is also quite different.
Just because the part is more expensive it is not necessarily better in any application.
The FET inputs behave much different from bipolar ones, they are much more sensitive to damage when handling. They are meant for high impedance sources, which are quite rare in Audio.
Temperature stability is not as good and the part might get hot and be unstable.
The noise is higher, especially at low frequencies .
The output swing limitation is not symmetrical and lower than the bipolar.
5534 has +/-22V max rail voltage vs. only 18V.
The transient behaviour is also quite different.
Last edited:
I think you'll be fine doing that substitution. With the caveat of the maximum rail voltages not being exceeded.
FET input opamps can normally be substituted for bipolar ones, the reverse is less likely to work.
FET input opamps can normally be substituted for bipolar ones, the reverse is less likely to work.
They are not direct replacements.
As well as the other points already mentioned you need to look whether the 5534 uses pins 1,5 and 8 in any way. If it does then the OPA627 would not be suitable without you modifying the circuit.
As well as the other points already mentioned you need to look whether the 5534 uses pins 1,5 and 8 in any way. If it does then the OPA627 would not be suitable without you modifying the circuit.
NE5534 used in a noise gain below 3 needs a compensation cap between pin5 and pin8. As pin 8 is unconnected on OPA627 this will be of no concern.
Valid point although it could be argued that leaving a cap in place (even if isolated at one end) is a possible means of introducing unwanted input/stray pickup into pin 5.
That probably is sweating the fine print 🙂 but the answer to the OP is that unless they understand all the details involved then the simple answer has to be that they are not interchangeable.
That probably is sweating the fine print 🙂 but the answer to the OP is that unless they understand all the details involved then the simple answer has to be that they are not interchangeable.
No particular specification in an opamp data sheet is going to tell you whether two different ones are interchangeable. It comes down to what the individual circuit is doing and how the designer implemented and physically laid out the circuit, which is outside of the opamp manufacturer's control.
It's likely that at least some of the difference perceived in 'sound' of opamps comes from when different ones are inappropriately substituted for another, causing instability and poor transient response of the circuit. Many opamps will oscillate when put into a circuit that wasn't designed aout that particular. Although it's likely the oscillation will be ultrasonic, it can affect the performance and distortion of the opamp in the audio band.
It's likely that at least some of the difference perceived in 'sound' of opamps comes from when different ones are inappropriately substituted for another, causing instability and poor transient response of the circuit. Many opamps will oscillate when put into a circuit that wasn't designed aout that particular. Although it's likely the oscillation will be ultrasonic, it can affect the performance and distortion of the opamp in the audio band.
If you can provide a schematic or even the model of the device you have, there might be better answers here.
The answers so far have been remarkable in the considerations that you all have made to what is obviously a difficult/complicated question. Thank you all for taking the time to answer. I especially appreciate the answers of those who have tempered their advice with practical experience.
Very simply to those who have answered already: I would would be using them in a Pioneer PD 91/PD3000 (Japanese version) cd player. Schematics are available to anyone who wants to take the time to look. Le' me know.
Very simply to those who have answered already: I would would be using them in a Pioneer PD 91/PD3000 (Japanese version) cd player. Schematics are available to anyone who wants to take the time to look. Le' me know.
So...
It does use a compensation cap (the 22pF). If you want to try the OPA627 then I would remove that cap.
You should also check the offset voltage by measuring the DC voltage across C534 and C533 and if the caps are reverse biased then remove and refit the cap the other way around so the polarity matches the offset.
And as always... you really should use a scope to check all is well afterward. This was an NE5534:
Swapping Op-Amps... you have checked to see it's stable haven't you ?
It does use a compensation cap (the 22pF). If you want to try the OPA627 then I would remove that cap.
You should also check the offset voltage by measuring the DC voltage across C534 and C533 and if the caps are reverse biased then remove and refit the cap the other way around so the polarity matches the offset.
And as always... you really should use a scope to check all is well afterward. This was an NE5534:
Swapping Op-Amps... you have checked to see it's stable haven't you ?
Attachments
No need, the OPA627 has no internal connection to pin 8. If you think it might pickup noise I suppose you could remove it, but 22pF caps are not large, and I suspect there's no issue.
Last edited: